Capulet never changed his mind about the marriage. From the start, he was approving of the match and encouraging of Juliet's suitor. In Act 1.2.16-22, Capulet says:
But woo her, gentle Paris, get her heart,
My will to her consent is but a part,
And she agreed, within her scope of hoice
Lies my consent and fair according voice.
This night I hold an old accustomed fast
Whereto I have invited many a guest
Such as I love, and you among the store.
When Tybalt is slain by Romeo, Lord Capulet erroneously believes that a hastened marriage to Paris will cure his melancholy daughter. In Act 3.4.13-16, Capulet pleads:
Sir Paris, I will make a desperate tender
Of my child's love. I think she will be ruled
In all respects by me; nay, I doubt it not.
Lord Capulet, blind as ever, believes until the bitter end that his daughter will ultimately follow his "will."